1. Field of the Invention
The present invention involves methods for regeneration and performance of a particulate filter of an internal combustion engine, especially a particulate filter of a compression-ignited internal combustion engine which is also termed a diesel engine.
2. Description of the Related Art
Exhaust emissions, to include particulate matter such as soot, of internal combustion engines are being reduced due to governmental regulations for health and environmental concerns. Particulate matter can be reduced in diesel engines by placing a diesel particulate filter in the exhaust system of the engine. The buildup of particulate matter in a particulate filter needs to be oxidized or combusted at regular intervals in a controlled process to keep engine back pressure low so that the engine operates efficiently and to avoid the release over a short period of time of large amounts of heat from soot combustion so that the particulate filter is not thermally damaged. Methods of regenerating a particulate filter by combustion of the accumulated particulate matter such as soot in a controlled process include a) systems that periodically raise the temperature of the exhaust emissions from the engine or the temperature of the particulate filter or b) using a particulate filter that contains a catalyst, such as an oxide of cerium or vanadium, to reduce the ignition temperature for combustion of particulate matter where the catalyst is added to the filter during its manufacture or introduced to the filter from a fuel during engine operation. Diesel engines, to include heavy duty diesel engines, are being equipped with an exhaust gas recirculation (EGR) system to meet governmental regulations for reduced emissions of nitrogen oxides or NOx. The inclusion of an EGR system on a diesel engine results in increased emissions of soot from the engine into the exhaust system and puts an increased burden on a diesel particulate filter to function efficiently in controlling/preventing tailpipe soot emissions. The presence of engine lubricant derived ash in a particulate filter has generally been considered to be deleterious to the performance of the filter. The engine lubricant derived ash can result from the combustion of metal and/or boron containing additives present in an engine oil that enter the combustion chamber and form a metal and/or boron containing ash deposit in the filter.
Huang et al. in U.S. Pat. Nos. 5,344,467 and 5,562,742 disclose organometallic complexes that can be used in diesel fuels for operating diesel engines equipped with exhaust system particulate traps.
Krutzsch et al. in U.S. Pat. No. 5,522,905 disclose a diesel fuel that contains an additive which improves the combustion of soot.
Barr et al. in U.S. Pat. Nos. 5,912,190 and 6,056,792 disclose a process of improving combustion of fuel and/or improving oxidation of carbonaceous products derived from the combustion of the fuel by including in the fuel prior to its combustion a Group I and/or Group II organo-metallic complex.
Caprotti et al. in International Publication No. WO 00/58422 disclose a fuel oil composition that comprises a) a neutral alkaline earth metal compound and/or a neutral alkali metal compound and b) a transition metal compound.
Roos et al. in European Publication No. EP 1378560A2 disclose aqueous additives in hydrocarbonaceous fuel combustion systems where the aqueous additive comprises one or more inorganic or organic metal compounds to include alkali, alkaline earth and transition metal compounds.
Methods for regeneration and performance of a particulate filter, especially a diesel particulate filter, have now been found that unexpectedly comprise lubricating an internal combustion engine with a lubricant composition that comprises additives that deliver ash to the particulate filter.